Degradation of cyanogenic glycosides during the processing of high quality cassava flour (HQCF)

Abstract

Cyanide degradation during HQCF processing was investigated. Two unit operations, namely; size reduction and drying were considered as the major factors in detoxifying cassava during processing. Six cassava varieties were processed into flour, either by grating or slicing, followed by drying by solar or mechanical means. Cyanide content of fresh, grated and sliced cassava, as well as the final HQCF was determined by alkali titration. Cyanogen content varied widely among varieties and ranged from 5.24 to 12.01 mgHCN/kg with a mean of 7.79 mgHCN/kg. A general trend of higher reduction in cyanide content was observed in grating as compared to slicing. Mean cyanide content were 2.65 and 3.49 mgHCN/kg for grated and sliced cassava respectively. Most of the change in amount of cyanide for HQCF under slicing occurred during drying, while most it was expelled after pressing, when grating was used. A 2-way interaction of the main factors also showed a marked improvement in cyanide reduction. Better detoxification was established in solar drying as opposed to mechanical drying, since flours from the latter were generally higher in cyanide and with a mean of 3.28 mgHCN/kg compared to the former with a mean of 2.87 mgHCN/kg. Findings of this study highlight the need for better disintegration and longer drying for better detoxification of the cyanogenic glycosides